1. Field of the Invention
The present invention relates to an optical lens system-driving control apparatus. More specifically, the present invention relates to a driving control apparatus which is incorporated in a camera having a plurality of lens groups movable in the optical axis direction and which microscopically drives the lens groups, for the purpose of zooming or focusing. The present invention also relates to a driving control apparatus which is used with a lens barrel having a plurality of lens groups and which microscopically drives the lens groups independently of one another.
2. Description of the Related Art
In general, an optical lens system including a plurality of lens groups is driven by employing a cam cylinder. In the case where the cam cylinder is employed, the movement of each lens group is dependent on the shape of the cam. However, since it is difficult to provide the cam with a complicated shape, the lens groups cannot be moved in such a complicated manner as is required in a recently-developed compact and multi-function camera.
If the lens groups are driven by their respective motors, they can be moved in a complicated manner. However, the movement of the lens groups has to be controlled with high accuracy. If not, the lens groups may obstruct each other or collide with each other In addition, another problem may occur, as will be discussed below.
The conventional techniques and the entailed problems will be considered, referring to the photographing lens and lens barrel employed in a camera.
A photographing lens having a zooming or focusing function is employed in a certain type of camera. In the photographing lens, the pin provided on the frame of each lens element is guided along the cam groove formed in a cam cylinder, and the positional relationships among the lens elements are determined by utilization of the cam groove. In order to perform zooming or focusing in an optimal manner and to produce a high-quality image, the positional relationships among the lens elements are ensured beforehand in relation to the cam groove. The cam cylinder is driven for zooming or focusing, by manually rotating the control ring mechanically associated with the cam cylinder or by means of a motor mechanically associated with the cam cylinder.
In U.S. Pat. No. 4,161,756, an actuator is provided for each one of lens groups, and the lens groups are driven independently of one another.
With the recent remarkable progress in the electronic technology, it has become possible to drive the lenses of a camera with high accuracy by mean of actuators of various types. Further, it has become possible to automatically control the driving of the lenses in accordance with the outputs of both an auto focus sensor and an electronic manual-operation dial. As a result of these, the driving time of the lenses has been shortened, and the control of the driving of the lenses has been made easier to perform.
At the same time, however, the load which is applied to the battery (i.e., a D.C. power supply) incorporated in the camera or provided for the photographing lens has been increased. In particular, the actuators consume a large amount of power. Moreover, since a number of lens groups are driven at one time, with the cam cylinder rotated, a large amount of power is required at one time, thus shortening the life of the battery. This problem may be solved by slowly driving the actuators, but this way for solving the problem inevitably results in a long driving time.
To solve the above problem, one lens group may be driven by its own high-speed actuator such that the driving timing of that lens group is shifted from that of another. In this case, however, it is likely that the lens groups will dynamically interfere with one another, if their positional ranges overlap with one another. In the case of e.g. a TTL camera, the positional relationships among the lens groups may deviate greatly from the positional relationships intended at the time of design, if the lens groups are driven for a long distance. In the worst case, the lens groups may collide with one another. If this happens, the image observed through the viewfinder is greatly affected. As a result, the operator looking into the viewfinder may feel unpleasant, and think it difficult to accurately operate the operation members while looking into the viewfinder.
The lens barrel of a camera contains a plurality of lens groups. Conventionally, a cam groove along which the lens groups are moved is formed in a single cylinder, and the lens groups are driven, with their predetermined positional relationships maintained, by rotating or linearly moving the single cylinder. However, since it is not easy to form a cam groove having such a complicated shape as corresponds to desirable movement of the lens groups, the manufacturing cost is inevitably increased. In an effort to provide a solution to this problem, U.S. Pat. No. 4,161,756 referred to above discloses a lens barrel having no cam groove. According to this U.S. patent, the positional relationships among a plurality of lens groups are stored in a storage means (such as a ROM) as digital-value data. On the basis of the digital-value data and the positional information obtained by actual measurement, the lens groups are driven independently of one another.
According to the above U.S. patent, the lens groups contained in the lens barrel attain intended positional relationships after they have been moved to their respective positions. However, they do not necessarily maintain desirable positional relationships during their movement. Therefore, in the case where focus detection is performed by using the light which represents the image of a subject and coming through the photographing lens, the lens groups have to attain the intended positional relationships, before starting the focus detection.